Some very good advice by everybody. KBacon hit on a couple things. Draw length and peak weight can play havoc with aiming, especially if the draw length is too long, which is very very common. Tweaking draw length can be critical for steady aiming. There is always a sweet spot where you'll be rock steady. Even 1/8" can sometimes make a heck of a difference.

Couple that with too much weight and things can get ugly. Target panic can creep up on you. The trick to this is to recognize it and admit that it is happening. We are all susceptable to it. The idea is to NOT deny it. If you do then you'll end up forcing the issue and making things worse.

Best idea? Tweak the draw length, lighten up the weight, and learn to aim the bow. Train the brain, because that's where the problems arise.
Work on shooting form---one arrow at a time. Learn to shoot the bow. Let the bow shoot the arrow.